This invention pertains to open web type trusses used in the construction of earthquake resistant buildings.
The special moment truss frame of this invention is seen to be a replacement for the wide-flange steel beams currently utilized in moment resisting frame construction techniques. This invention arose, after a University of Michigan study that resulted in a study of a draft guide for designing special momentxe2x80x94resisting truss frames was released. This study outlined the problems to be overcome, and the inventor of this application has found one means to solve those problems.
More specifically, the structural engineering world has been shifting to what is known as xe2x80x9cperformance based designxe2x80x9d wherein the energy of a seismic event is absorbed by the structure, such that a certain amount of deformation of the structure transpires as a result of the seismic event, but the superstructure while undergoing deformation and deflection, survives the seismic event such that the building remains standing, subsequent to the seismic event. Then after things calm down, replacement components can be put into place as may be determined to be structurally beneficial, while the building is being utilized. The invention of this application is based upon the concepts embodied in performance based design.
This is a totally different thought process from the previous approach, of creating a building structure to limit the deformation, i.e., stand tall and erect and not be influenced by the seismic event. Performance based design operates on the premise that it""s OK to deform and deflect, so long as the building does not fall. The truss of this invention employs this new approach in its engineering.
In today""s cost competitive world, cost savings over prior art truss designs were desired. Therefore during the development stage, means were looked at to eliminate plates and welded connections wherever possible to achieve these cost savings.
Bearing all of this in mind, and being knowledgeable of the seismic event criteria to be included in the design of a new truss, that would permit a certain amount of deformation, yet would permit the building to continue to stand after a seismic event, the truss of the invention came to be.
It is one object of this invention to provide a new type of truss.
It is a second object to provide a new truss that is particularly applicable to utilization in Zone 4, ie. highly susceptible seismic geographic areas.
It is a third object to provide a truss which when utilized can shorten construction time, and reduce the cost of construction of the building.
It is a forth object to provide a construction technique that eliminates many welding steps and the associated inspection efforts related thereto.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the device possessing the features properties and the relation of components which are exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the appended claims.